1. Field of the Invention
The present invention relates to an improved ratcheting mechanism adapted for use with a screwdriver and, more particularly, to a ratcheting screwdriver which provides three modes of operation, including ratcheting modes in forward and reverse directions and a non-ratcheting mode.
2. Description of the Prior Art
There are a number of prior art disclosures directed to the use of ratchet mechanisms in conjunction with hand tools--particularly wrenches which employ a handle mechanism substantially perpendicular to the axis of rotation of the tool. The use of a ratchet mechanism in conjunction with screwdrivers entails design constraints in terms of compactness of the ratchet mechanism. Such constraints are made all the more difficult when the tool is a miniature screwdriver of the type most appropriately used to tighten and loosen the very smallest type screws, as well as hard to reach screws, such as screws used on dental prosthodontic devices and the like.
U.S. Pat. No. 4,466,523 to De Carolis et al. generally discloses a ratchet handle for a miniature screwdriver which employs a pair of opposing pawls which are biased by a spring and which selectively engage teeth at the interior of a cylindrical structure to provide a three-mode ratchet drive. A shifter engageable at one of three positions has so-called ears which selectively interact With the pawls. In one embodiment, three pairs of opposing pawls are biased by a garter spring. In a second embodiment, an integral serpentine spring/pawl assembly is employed to provide ratcheting in the selected direction mode. Both constructions involve the use of components whose geometry is very complex. As a result the cost of manufacturing miniature screwdrivers of this type is high and manufacture is difficult.